Methods and compositions for improved electrophoretic display performance

Abstract

The invention is directed to novel methods and compositions useful for improving the performance of electrophoretic displays. The methods comprise adding a high absorbance dye or pigment, or conductive particles or a charge transport material into an electrode protecting layer of the display.

1 . A method for improving performance of an electrophoretic display, which method comprises adding a charge transport material to one of the electrode protecting layers of the electrophoretic display.  
   
   
       2 . The method of  claim 1  wherein said charge transport material is a hole transport material having an oxidation potential less than 1.4 V (vs SCE).  
   
   
       3 . The method of  claim 2  wherein said hole transport material has an oxidation potential less than 0.9 V (vs SCE).  
   
   
       4 . The method of  claim 3  wherein said hole transport material has an oxidation potential ranging from 0.5 to 0.9 V (vs SCE).  
   
   
       5 . The method of  claim 2  wherein said hole transport material is selected from the group consisting of pyrazolines, hydrazones, oxazoles, oxadiazoles, enamines, carbazoles, arylamines, triarylmethanes, biphenyls, dienes, dienones, triazoles, metal phthalocyanines, metal naphthalocyanines and oligomeric or polymeric derivatives thereof, and mixtures thereof.  
   
   
       6 . The method of  claim 5  wherein said pyrazoline is 1-phenyl-3-(4′-dialkylaminostyryl)-5-(4″-dialkylaminophenyl)pyrazoline.  
   
   
       7 . The method of  claim 5  wherein said hydrazone is p-dialkylaminobenzaldehyde- N,N-diphenylhydrazone, 9-ethyl-carbazole-3-aldehyde-N-methyl-N-phenylhydrazone, pyrene-3-aldehyde-N-N-diphenylhydrazone, 4-diphenylamino-benzaldehyde-N,N-diphenylhydrazone, 4-N,N-bis(4-methylphenyl)-amino-benzaldehyde-N,N-diphenylhydrazone, 4-dibenzylamino-benzaldehyde-N,N-diphenylhydrazone or 4-dibenzylamino-2-methyl-benzaldehyde-N,N-diphenylhydrazone.  
   
   
       8 . The method of  claim 5  wherein said oxazole or oxadiazole is 2,5-bis-(4-dialkylaminophenyl)-4-(2-chlorophenyl)oxazole, 2,5-bis-(4-N,N′-dialkylaminophenyl)-1,3,4-oxadiazole, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,2,3-oxadiazole, 2,2′-(1,3-phenylene)bis[5-[4-(-(1,1-dimethylethyl)phenyl] 1,3,4 oxadiazole, 2,5-bis(4-methylphenyl)-1,3,4-oxadiazole or 1,3-bis(4-(4-diphenylamino)-phenyl-1,3,4-oxadiazol-2-yl)benzene.  
   
   
       9 . The method of  claim 5  wherein said enamine, carbazole or arylamine is bis(p-ethoxyphenyl)acetaldehyde di-p-methoxyphenylamine enamine, N-alkylcarbazole, trans-1,2-biscarbazoyl-cyclobutane, 4,4′-bis(carbazol-9-yl)-biphenyl, N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1-bi[phenyl]-4,4′-diamine, 4,4′-bis(N-naphthyl-N-phenyl-amino) biphenyl (or N,N′-di(naphthalene-2-yl)-N,N′-diphenyl-benzidine);4,4′,4″-trismethyl-triphenylamine, N-biphenylyl-N-phenyl-N-(3-methylphenyl)-amine, 4-(2,2-bisphenyl-ethen-1-yl)triphenylamine, N,N′-di-(4-methyl-pheny)N,N′-diphenyl-1,4-phenylendiamine, 4-(2,2-bisphenyl-ethen-1-yl)-4′,4″-dimethyl-triphenylamine, N,N,N′N′-tetraphenylbenzidine, N,N,N′,N′-tetrakis(4-methyphenyl)-benzidine, N,N′-bis-(4-methylphenyl)-N,N′-bis-(phenyl)-benzidine, 4,4′-bis(dibenz-azepin-1-yl)-biphenyl; 4,4′-bis(dihydro-dibenz-azepin-1-yl)-biphenyl, di-(4-dibenzylamino-phenyl)-ether, 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)cyclohexane, 4,4′-bis(n,N-doiphenylamino)-quaterphenyl, N,N,N′,N′-tetrakis)naphtha-2-yl)benzidine, N,N′-bis(phenanthren-9-yl)-N,N′-bis-phenyl-benzidine, N,N′-bis(phenanthren-9-yl)-N,N′-bis-phenyl-benaidine, 4,4′,4″-tris(carbazol-9-yl)-triphenylamine, 4,4′,4″-tris(N,N-diphenylamino)-triphenylamine, 4,4′-bis(N-(1-naphthyl)-N-phenyl-amino)-quaterphenyl, 4,4′,4″-tris(N-(1-naphthyl)-N-phenyl-amino) triphenylamine or N,N′-diphenyl-N,N′-bis(4′-(N,N-bis(naphthy-1-yl)-amino)-biphenyl-4-yl)-benzidine.  
   
   
       10 . The method of  claim 5  wherein said triarylmethane or biphenyl is bis(4-N,N-dialkylamino-2-methylphenyl)phenylmethane or 4,4′-bis(2,2-diphenyl-ethen-1-yl)-biphenyl.  
   
   
       11 . The method of  claim 5  wherein said diene or dienone is 1,1,4,4-tetraphenyl-butadiene, 4,4′-(1,2-ethanediylidene)-bis(2,6-dimethyl-2,5-cyclohexadien-1-one), 2-(1,1-dimethylethyl)-4-[3-(1,1-dimethylethyl)-5-methyl-4-ox-2,5-cyclohexa-dien-1-ylidene]-6-methy-2,5-cyclohexadien-1-one, 2,6-bis(1,1-dimethylethyl)4-[3,5-bis(1,1- dimethylethyl)4-oxo-2,5-cyclohexa-dien-1-ylidene]-2,5-cyclohexadien-1-one or 4,4′-(1,2-ethanediylidene)-bis(2,6-(1,1-dimethyl-ethyl)2,5-cyclohexadien-1-one).  
   
   
       12 . The method of  claim 5  wherein said triazole is 3,5-bis(4-tert-phenyl)-4-phenyl-triazole or 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole.  
   
   
       13 . The method of  claim 5  wherein said metal phthalocyanine or naphthalocyanine is Cu phthalocyanine, Cu naphthalocyanine or an alkylated derivative thereof.  
   
   
       14 . The method of  claim 1  wherein said charge transport material is an electron transport material.  
   
   
       15 . The method of  claim 14  wherein said electron transport material is selected from the group consisting of electron deficient compounds in the general classes of fluorenones, nitro and nitrile compounds and oligomeric or polymeric derivatives thereof, and mixtures thereof.  
   
   
       16 . The method of  claim 14  wherein said electron transport material is 2,4,7-trinitro-9-fluorenone, 2-(1,1-dimethylbutyl)-4,5,7-trinitro-9-fluorenone, (4-butoxycarbonyl-9-fluorenylidene)malononitrile, 2,6-di-tert-butyl-4-dicyanomethylene-4-H-thiopyran-1,1-dioxide,2-(4-(1-methyl-ethyl)-phenyl)-6-phenyl-4H-thiopyran-4-ylidene]-propanedinitril-1,1-dioxide or 2-phenyl-6-methylphenyl-4-dicyanomethylene-4-H-thiopyran-1,1-dioxide or 7,7,8,8-tetrachcyanonquinodimethane.  
   
   
       17 . An electrode protecting layer composition for an electrophoretic display which composition comprises a charge transport material.  
   
   
       18 . The composition of  claim 17  wherein said charge transport material is a hole transport material or an electron transport material.  
   
   
       19 . The composition of  claim 17  wherein said charge transport material is 4-(dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran, bis(2-2-hydroxyphenyl)-benz-1,3-thiazolato)-Zn complex, bis(2-(2-hydroxyphenyl)-benz-1,3-oxadiazoleato)-Zn complex, tris(8-hydroxy-chinolinato)-Al complex, tris(8-hydroxy-4-methyl-chinolinato)-Al complex or tris(5-chloro-8-hydroxy-chinolinato)-Al complex.  
   
   
       20 . The composition of  claim 17  which is a primer layer composition comprising a thermoplastic, thermoset or a precursor thereof and a charge transport material.  
   
   
       21 . The composition of  claim 20  wherein said thermoplastic or thermoset material is selected from the group consisting of polyvinylbutyral, cellulose acetate butyrate, poly (alkyl acrylates), poly(alkyl methacrylates), polyethers, polyurethanes, polyamides, polyesters, polycarbonates, multifunctional acrylates or methacrylates, vinylbenzenes, vinylethers, epoxides and oligomers or polymers thereof, and mixtures thereof.  
   
   
       22 . The composition of  claim 17  is a sealing layer composition comprising a sealing material and a charge transport material.  
   
   
       23 . The composition of  claim 22  wherein said sealing material is selected from the group consisting of thermoplastic elastomers, polyvalent acrylate or methacrylate, cyanoacrylates, polyvalent vinyl, polyvalent epoxide, polyvalent isocyanate, polyvalent allyl and oligomers or polymers containing crosslinkable functional groups, and mixtures thereof.  
   
   
       24 . The composition of  claim 22  wherein said sealing layer composition has a specific gravity lower than that of the electrophoretic fluid filled in the display cells of said electrophoretic display.  
   
   
       25 . The composition of  claim 22  wherein said sealing alyer composition is hardened in situ.  
   
   
       26 . The composition of  claim 17  which is an adhesive layer composition comprising an adhesive material and a charge transport material.  
   
   
       27 . The composition of  claim 26  wherein said adhesive material is selected from the group consisting of acrylics, styrene-butadiene copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, polyvinylbutyral, cellulose acetate butyrate, polyvinylpyrrolidone, polyurethanes, polyamides, ethylene-vinylacetate copolymers, epoxides, multifunctional acrylates, vinyls, vinylethers and oligomers, polymers and copolymers thereof, and mixtures thereof.  
   
   
       28 . The composition of  claim 17  wherein said charge transport material is in the amount of from 0.1 to 30% by weight of the total solid content of the electrode protecting layer.  
   
   
       29 . The composition of  claim 28  wherein said charge transport agent is in the amount of from 2 to 20% by weight of the total solid content of the electrode protecting layer.  
   
   
       30 . An electrophoretic display comprising at least one electrode protecting layer formed of a composition comprising a charge transport material.  
   
   
       31 . The electrophoretic display of  claim 30  which is prepared from the microcup technology.